Geographic Regions (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenue	$ 54,677	$ 47,760	$ 32,944	$ 29,135	$ 42,409	$ 33,342	$ 22,483	$ 22,074	$ 164,516	$ 120,308	$ 104,883
Operating income (loss)									10,425	(7,908)	(13,521)
Net long-lived assets	15,792				15,960				15,792	15,960
The Netherlands
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenue									81,443	52,189	46,982
Operating income (loss)									5,206	(7,773)	(9,069)
Net long-lived assets	5,190				4,996				5,190	4,996
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenue									60,952	44,299	37,483
Operating income (loss)									1,527	(1,396)	(5,541)
Net long-lived assets	9,924				10,171				9,924	10,171
France
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenue									5,588	8,758	8,387
Operating income (loss)									(1,000)	(783)	(330)
Net long-lived assets	289				241				289	241
China
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenue									12,673	11,799	9,725
Operating income (loss)									3,647	1,530	986
Net long-lived assets	$ 389				$ 552				389	552
Other
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenue									3,860	3,263	2,306
Operating income (loss)									$ 1,045	$ 514	$ 433